Definitely build your own if at all possible. If you buy a pre-assembled weapon, you will almost surely decide to start changing out parts on it. Then you are just spending money on extra parts from the original purchase that will most likely end up never being used. Been there and done that. Learned my lesson. Don't forget that you are going to have to have access to a certain number of speciality tools also. You need to either consider this in your budget, or maybe find some you can rent/borrow.
